【なぜなら / なぜかというと】 meaning, formation and examples (JLPT N3 grammar)

Meaning

1Introduces the reason for a statement already made, placed at the start of the following sentence.Ex. 1
2In the なぜかというと form, it adds an explanation by first posing the question "why?" and then answering it.Ex. 2

Examples

1

彼女かのじょは来こないだろう。なぜなら、昨日きのう熱ねつを出だしたと聞きいたからだ。

She probably won't come. That's because I heard she had a fever yesterday.

2

この計画けいかくは見直みなおすべきだ。なぜかというと、現状げんじょうではコストが高たかすぎるからです。

This plan should be reconsidered. The reason is that, as things stand, the costs are too high.

Formation

なぜなら/なぜかというと＋，＋＋からだ/からですpoliteness depends only on whether the sentence ends in 「だ」 or 「です」; before 「から」 always use the plain form, e.g. 「来るからです」「高すぎるからです」

なぜなら/なぜかというと＋，＋Noun/＋だ＋からだ/からですe.g. 「学生だからです」

なぜなら/なぜかというと＋，＋＋のだ/のですfor a more emphatic tone

Politeなぜかといいますと＋，＋＋からですused in formal settings

Usage

Used in explanations, arguments, essays and speeches to justify a claim or conclusion stated just before. なぜなら has a somewhat formal, logical tone. なぜかというと sounds more like a spoken explanation. Unlike から or ので, which link cause and result within one sentence, this pattern splits them: result first, then reason.

Watch out

Learners often forget to close the reason clause with からだ or からです, which leaves the sentence sounding unfinished.

Do not put なぜなら before the result; the conclusion comes first, and なぜなら introduces the reason afterward.

Easily confused with

1.
というのはN3Placed at the start of a sentence, というのは likewise supplies the reason after the conclusion, with からだ／のだ at the end, so the two are interchangeable, though というのは sounds more casual than なぜなら. It can also follow a word or phrase to introduce a topic or give a definition, which this pattern cannot.
2.
からN5から is similar only when expressing cause: it attaches directly to a clause, can put the reason first with a request, conjecture, etc. following, or add the reason afterward as 〜からです. なぜなら must open a new sentence after the conclusion and usually ends in からだ.
3.
のでN5ので attaches to the end of a clause, putting the reason before the result with a softer tone, while なぜなら opens the following sentence, giving the conclusion first and then the reason with からだ. They can't be swapped directly, and switching requires reversing the order.
4.
からこそN2からこそ follows a cause clause, reason before result, and stresses that it is precisely this reason; this pattern opens the second sentence, with the conclusion first and the reason added in a new sentence ending in からだ. The two are not directly interchangeable.
5.
ことからN2ことから follows the preceding element, reason before result, to explain the origin of a name or the basis for a judgment, and is rather formal; なぜなら adds the reason in a new sentence after the conclusion, ending in からだ. Their order is reversed, so one can't directly replace the other.
6.
せいでN3せいで follows noun + の, verbs, etc. to mark a cause, mostly for bad outcomes and with a tone of blame; なぜなら adds the reason in a new sentence after the conclusion and works for good or bad results. They can't be directly substituted.

というのは also opens an explanatory sentence but is more conversational. から and ので attach directly to a clause to give a reason within one sentence. からこそ stresses "precisely because"; ことから marks the evidence behind a judgment or name; せいで attributes a negative result to a cause.

Say it right, write it right